Jon.....
?
Honestly, I don't even know what type of LED I have
and bought these because of their ultra-bright characteristics from a surplus
electronics component shop at US$ 1.20 for 30 pieces. ?Overdriving
the? LED is done?on purpose to give the high visibility and intensity
that I am looking for.? How long these LED will last is another story. I
would expect the LED on the brake light will last longer as these are only
switch on intermitently during braking while the back light is switch on all the
time. As the system is of an experimental project, I might have to make changes
to ensure more reliability over time.
?
My scooter is running with 2x12volt/12ah SLA
battery connected in series for 24volt operation. Perhaps, an additional?12
volt voltage regulator circuit stepping down from the 24 voltage system would
help to stabilise voltage.
?
Thank you for your comments and
regards.
?
Bob Wong - Singapore
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----- Original Message -----
Sent: Thursday, August 02, 2001 8:56
AM
Subject: Re: [Electronics_101] Newbie LED
question
Robert,
?
Depending on the type of LED you are using, let's
assume that Vf is 2V - so when you put 5 of
them in series, you have an actual voltage drop of 10V, leaving you 2V
in?excess ... so in actual fact you are over-driving your LED's by
0.4V?(say 20% per each) for short periods of time - no big deal, it will
reduce the life of your LED's somewhat, but probably not enough to notice. I
will agree that it is a slightly more efficient usage of current, in that you
are not dissapating 16 seperate lots of heat - certainly a
potential?issue when you are running on limited supply
source.
?
?
If you are using it on a scooter another thing to
point out would be that if you are running it on the main drive batteries,
when in use the voltage at the terminals will actually be a lot less that 12V,
if you are running it on a seperate?battery, as the battery discharges
you will be running closer to the 10V mark too, and so getting closer to the
LED's capabilities.
?
l8r
?
Jon
----- Original Message -----
Sent: Thursday, August 02, 2001 8:17
AM
Subject: Re: [Electronics_101] Newbie
LED question
I have been experimenting using leds
for?lighting system on my electric scooter and have?built a
combined back/brake light with 3 rows of 5 red leds in series operating on
12 volts SLA. The brake light is connected parallel 2 rows of 5 leds in
series and the back light is1 row of 5 leds in series. Current draw is
approx. 90ma for the brake light and 45ma for the back light (total current
draw=135ma). No current limiting resistors were? used and the leds are
operating at maximum light intensity. I have used the light for more than 6
months and did not encounter any problem, the circuit diagram is posted
below should you be interested.
?
?
Bob Wong - Singapore
----- Original Message -----
Sent: Thursday, August 02, 2001 4:08
AM
Subject: Re: [Electronics_101] Newbie
LED question
16 x 30mA = 480mA.?? Therefore, the 12V source must be able
to put out half an amp for the LEDs.
?
half an amp!? That's as
much as a television draws!? Wow...
?
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